The present invention relates in general to the construction of ball joints and in particular to a new and useful axial ball joint construction which is particularly suited for use in a motor vehicle and which utilizes a housing having a rim zone which is thicker in its accumulation of material than areas of the housing deeper into a socket which is defined by the housing for accepting a ball of the ball joint. This thicker area is crimped inwardly to securely hold the ball in the socket.
German patent application No. 26 55 353 and German utility model No. 77 18 994 describe a joint of this kind. To assemble such a joint, the ball part is inserted by its ball portion and with a resilient socket, into a housing and then locked therein by bending the housing rim inwardly, so that the housing remains cylindrical on its outside, only is crimped in along its rim.
To mount a ball joint in a vehicle mechanically, the housing of the joint must be throughout cylindrical and have a round, angular, or irregular cross section, i.e. the housing must not have any portions which would protrude outwardly beyond a cylindrical contour, but must have the same cross sectional portions which recede inwardly therefrom.
The axial loading capacity of such a ball joint is given by the material strength of the bent-in housing rim, so that conventional axial ball joints having an outer cylindrical housing and a constant wall thickness on their rim, can be loaded only within narrow limits. The tear-out force acting in the axial direction of the joint shank encounters only limited opposition which is exerted by the end rim. In conventional designs, the material thickness in the rim zone is determined by the inside surface of the housing, which, before the accomplished assemblage, is also cylindrical, up the equatorial plane of the ball.
From German No. OS 27 58 906 (equivalent to U.K. patent application No. 2,004,321) and other references, axial joints are known in which the housing rim at the shank side is formed by a wall portion which is somewhat thicker than the main housing portion having a cylindrical surface. This increases the resistance to tearing out the ball part. These prior art joints, however, are assembled by inserting the ball part into the housing from the rear, which does not require a bending of the housing rim at the shank side.